Predetermined force-travel tool



M rch 1, 1960 H. P. DUPRE PREDETERMINED FORCE-TRAVEL TOOL 4 Sheets-Sheet 1 Filed May 1, 1958 INVENTOR Hen/fly PDu m e ATTOR EY March 1, 1960 DUPRE I 2,926,556

PREDETERMINED FORCE-TRAVEL TOOL Filed May 1, 1958 4 Sheets-Sheet 2 FIG.3

BY JAWS ON CONNECTOR (LBS) /7 .900 .800 .700 .600 .500 .40 .300 .200 .IOO .000 JAW OPENING AT CRIMPING GROOVE (INCHES) FORCE E 5 FIG. 5

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POINT o|= FORCE. APPUCATION (F FIG. 7

March 1, 1960 H. P. DUPRE 2,926,556

PREDETERMINED FORCE-TRAVEL TOOL Filed May 1, 1958 v r 4 Sheets-Sheet 4 A 80cc 'IOOO FORCE TRAVEL cuzvas 2 5. FIG. 8 5000 II a z POINT c 40 f 3 cuzvz c I 2 NEW CAM I -'$OOO 9 TYPE TOOL. l

3 l I N I l 2000 CURVE D fi I u PRIOR ART TO66L TOOL at Q 1000 E POINT c,

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a DISTANCE FROM TOOL cslv'ruzuue TO J'Aw- HANDLE. PIVOT FOR 705 1.5 PIVOT DISPLACEMENT ounuuq CONNEC cg cRIMPuuq (INS).

INVENTOR HENRY P. DUPRE ATTORNEY United States Patent PREDETERMINED FORCE-TRAVEL TOOL Henry P. Dupre, Wilton, Conn., assignor to Burndy Corporation, a corporation of New York Application May 1, 1958, Serial No. 733,787

2 Claims. (Cl. 81-15) My invention relates to crimping and cutting tools operated with a single handstroke.

This is a continuation-in-part of my application Serial No. 458,406, filed September 27, 1954, and now abandoned.

Hitherto some tools used, for example, for crimping electrical connectors, employed the toggle principle involving fixed links, such as is illustrated in Patent No. 2,635,494.

I have plotted a force-travel curve typical of crimping tools, for example, using the toggle principle, and a similar curve showing the requiredforce needed for crimping electrical connectors. From the discrepancy between the two curves, I concluded that a new type of crimping tool was necessary in which the force-travel curve of the tool more nearly matched the force-travel curve required to compress the connectors, and accordingly the design of a tool having such predetermined force-travel curve is the principal object of my invention.

While hand operated tools are presently in use which will crimp large sized connectors, such tools have the disadvantage of requiring many strokes over a considerable period of time. Consequently, it is a further object to provide a single stroke compression tool capable of crimping electrical connectors to a size hitherto impossible with single stroke handtools.

Another object is to provide a tool having cutting jaws wherein the force-travel curve of the tool follows substantially the resistance curve of the bolt, cable or other article to be cut.

I accomplish these and other objects and obtain my new results, as will be apparent from the device described in the following specification, particularly pointed out in the claims, and illustrated in the accompanying drawings in which:

Fig. 1 is a plan view of my invention illustrated by way of example in a'single stroke crimping tool with the cover removed to show the mechanism.

Fig. 2 is a side elevation of the same, with cover and handle shown in section.

' Fig. 3 is a sectional view of Fig. 1 taken in plane 3-3.

Fig. 4 is a chart showing a comparison of different work curves involved for prior art toggle-type tools and for typical crimp-type electrical connectors.

Fig. 5 is a sectional view taken along the lines 55 of Fig. 3.

Fig. 6 is a line diagram of a typical prior art toggle type tool.

Fig. 7 is a graphic illustration of the input force travel curves for a typical prior art toggle type tool, the desired input force travel curve for the ideal tool and the actual input'force travel curve for the cam type tool of this invention.

Fig. 8 is a graphic illustration of a force travel curve for the typical prior art toggle tool and new cam type tool of this invention.

In Fig. 4 I haveshown curve A which was arrived at experimentally and represents a composite resistance travel curve for crimp-type electrical connectors. This composite curve represents the desiredwork curve of a crimping tool because it defines the output force (i.e. the force exerted by the jaws of the tool in the connector) needed at all points of jaw closure. This composite curve is independent of the means of closing the jaws of the tool on the connector. The area under curve A, measured in the coordinate units,.equals the useful output work required of a tool in order to satisfactorily crimp a connector onto a cable.

Of course, input work equals the output work plus losses. Input work also equals the input force times the distance it travels. Curve B represents a curve illustrating the work curve that is obtained using a typical prior art toggle mechanism as the force multiplier of a constant input force, the constant input force is the maximum force that a person can repetitively apply to a tool. Curve B can have an initial vertical rise, shown by the dotted line, since it may be assumed that the handle opening will be less than permitting an initial closing force to be applied. 7

Fig. 6 is a line diagram of a typical prior art toggletype tool. These tools are operated by applying a force (F on the handles, and this force is transmitted to the pivot and, in turn, to the jaws. The input torque about R in the toggle is equal to the input force times the vertical distance from the point of input force to the jaw output torque divided by the distance between the jaw-.

handle pivot and the toggle point.

In the normal toggle tool the distance between the jawhandle pivot and the toggle constantly variesin a decreasing manner as the jaws are closed. Thus assuming a constant input force applied to the handle, the normal prior art toggletool has the force-travel curve shown as curve D of Fig. 8.

Investigation of the force necessary to compress a typical connector onto a conductor yields a force-travel curve shown as curve C of Fig. 8. It should be noted that the areas under curve C and curve D are approximately equal, but that it is necessary to vary the input force when using a toggle tool to apply a compression connector. For example, if a constant input force is applied when the distance from the tool center line to the jaw handle pivot is approximately .2 inch,-the connector could not be criinped until approximately twice the input force is applied to transform point C on curve D to point C on curve C. It is thus readily apparent that when using a toggle type tool of the prior art, a constant input force cannot achieve the desired output. This is clearly represented by the curves shown in Fig. 7.

Fig. 7 illustrates the desired constant input force for a tool to compress electrical connectors. It is realized that for ease of operation, the workman should apply approximately 70 pounds of input force to the handles of the tool. In the ideal situation this 70 pounds of input force would remain constant throughout the tool cycle. However, as shown in Fig. 7, as an ordinary prior art toggle tool is utilized, the workman starts off applying less than 70 pounds of force and at one point during the cycle has to apply more than twice this amount in order to complete the connection. Again; the area under the work curves are approximately equal.

The applicant, having discovered these characteristics, set about inventing a tool which would more nearly achieve the purpose with the desired constant input. Returning to the formula above set out, it is noted. that the-output Patented Mar. 1, 19 0 force is dependent upon the denominator which is the distance between the jaw-handle pivot and the toggle point. Thus the applicant reasoned that this distance had to be altered from the usual curve of this distance versus handle deflection in the prior art toggle tool. When this is achieved the tool input force would more nearly approach the ideal input force curve. In order to do this, the applicant replaced the ordinary prior art toggle mechanism with a cam arrangement. These cams were so designed to have a profile with a plurality of different radii of curvatures so that when a constant force was applied to the handles of his tool, the output curve more nearly approximated the curve C of Fig. 8, not the curve D of Fig. 8, as did the previous tools. The cam surface was generated by transforming a constant input force into the desired output force. The relative rolling motion of the cam surfaces varies the distance between the point of contact and the force applying means in accordance with the cam surface previously arrived at.

It is clear from the prior art that when the toggle linkagecomprises two circular elements, the distance between the toggle pivot and the jaw handle pivot will vary proportionately to the movement of the handles, but in the applicants device the distance between the toggle pivot or contact point of the cam members and the jaw handle pivot varies in accordance with the cam profile. In other words, the distance between the point of contact of the cam and the jaw handle pivot constantly and instantaneously varies as the handles are closed.

The toggle mechanism force-travel curve of Fig. 8 assumes a tool of the same dimensions as the tool illustrated in Figs. 1 and 2. The input force was considered to be constant; however, if the input force varies, the output force-travel curve could shift and curve D would be made to overlie curve C. Since at any instant the output force is proportional to the input force, and it is desired (as shown above) to have curve D overlie curve C, then it is necessary to increase the input force accordingly. For example, the input force would have to be doubled if point C is to overlie point C Note, however, that since the constant input force used in arriving at curve D is the maximum repetitive force a person can apply, it is not sufficient to close the tool.

Starting with a constant input force which is the maximum repetitive force that a person can apply to the tool, a desired size for the tool with a given handle opening and having the output work needed (the area under curve C) and an assumed allowance for losses, I calculated the mechanical advantage needed for each point of jaw closure to translate curve D to curve C. The needed mechanical advantagesmay be considered as a series of instantaneous toggles of necessary proportions. Thus if the toggle tool of curve D could continuously and instantaneously have its toggles altered as the handles of the tool are closed, the desired tool would be achieved.

By plotting the necessary instantaneous toggles and connecting the plot by a smooth curve, a cam surface is generated which transforms the constant input force into a desired output force curve. Thus the tool of my invention is capable of utilizing a constant input force to operate on a mechanism over a given force-travel curve.

I thus achieve the maximum efliciency possible for connector crimping operations.

Additionally, by'using rolling cams, one on the other, I completely eliminate wear on the carnsas a result. of friction. The only sliding motions in the tool .are at thepins that act as pivots and the eccentric which may be easily adjusted to compensate for wear. The teeth extending from the cams maintain the cams in proper relative position. During the closing of the tool, the cams rotate and spread apart cammed ends of the jaw. A nearly uniform force applied to the handles is converted by the cams to the varying output force shown on the desired work curve.

.In-the drawings,ql have illustrated a crimping tool '10 as one of my invention. It comprises the cam handle assemblies 12 and 14, pivotally mounted at eccentric studs 16 and 18 to jaw members 20 and 22. At the other ends of the jaw members are the indenting or working surfaces, such as 24 to 31, and intermediate the two ends, the jaw members rotate on pins 32 and 34, respectively, connected by the links 36. An alignment pin 38 is positioned in grooves 40 and 42 between the two jaw members so that the indenting grooves will match when the tool is closed.

My invention makes use of two rolling cams 44 and 46, which replace the fixed toggles of previous tools. The two cams are kept synchronized by means of matching gears 48 and 50 positioned in slots 49 and 51 of the cams. Springs 52 and 54 are employed to keep the two cams in constant contact.

The spring used for keeping the two cams in constant contact has the additional advantage of continuously exerting a closing force on the jaws so that a connector inserted between the jaws may be maintained in position by the spring pressure without damage to or dropping of the connector when the operator applies both hands,

to the tool.

Eccentric studs 16 and 18, to which are threaded bolts 56 and 58, each provided with a washer 57, are used to connect the jaw members to the cams and to adjust the tool for wear and for manufacturing tolerances of the parts. The heads 60 of the studs are serrated for seating in the correspondingly serrated hole 61 in each cam. When each eccentric stud is unseated and rotated in the direction of arrow 63 stamped thereon, the eccentric surface 65 is moved with respect to the corresponding bore 67 in jaw member 22, and the rear end of the engaged jaw will move outwardly. Both eccentric studs must be adjusted equally to insure proper cam alignment. After adjustment, the eccentric studs are reseated back in the cams, and bolts 56 and 58 are tightened against bushing 62, which is force fitted into the hole 64 in each cam.-

A snap ring 66 positioned at the end of each bolt keeps the parts from disassembling during adjustment, and is accommodated in recess 68 of the eccentric when the eccentric is unseated for adjustment.

Press-fitted pins 70, 71, 72 and 73, with associated snap rings and washers, are employed to secure matching gears 48 and 50 to rolling cams 44 and 46, respectively. Instead of press-fitted pins, bolts and nuts could be used.

Pins 70 and 72 additionally project above the cams and.

operate in slots 74 and 76 of stop link 78. This prevents the, operator from disengaging the gears by opening the tool too far.

The ends of springs 52 and 54 are anchored about the pins 71 and 73 and maintained in position. Cover plates 80 may be in one piece, welded together or supported by screws 82 to each other may be placed over :the, mechanism to keep the parts clean and to prevent injury to the operator.

The handle assemblies 12 and 14 of tubular steel pro vided with rubber hand grips 13 and 15, as shown,.may be replaced by wood handles for use on energized ,lines.

The projecting tubular ends of the cams may be threaded.

and tapered for mounting the handles, as at 19, in Fig. 2.

When the handles 12 and '14 are opened, and thus-the jaws 20 and 22 are opened, the flat portions 84 and '86 of the earns 44 and 46 Qmeet, P even ing the handles :12

and 14 from being spread beyond a predetermined posh-v Since the cam contour presents:

Lav:

trative, and that the invention may be carried out in other ways without departing from the spirit of my invention, and, therefore, I claim broadly the right to employ all equivalent instrumentalities coming within the scope of the appended claims, and by means of which, objects of my invention are attained and new results accomplished, as it is obvious that the particular embodiments herein shown and described are only some of the many that can be employed to attain these objects and accomplish these results.

I claim:

1. A tool comprising a pair of movable jaws each having a jaw pivot, a work surface on one end of said jaw and an operating end on said jaw disposed on the opposite side of said pivot from said work surface, an inflexible link coupling said jaw pivots together, a jaw handle pivot coupled to the operating end of each of said jaws, a cam contact member associated with each of said jaws rotatable about said jaw handle pivots, means for applying force to cause a relative rolling motion by the said two cam members on each other to vary the distance between the point of contact of said cam members and said jaw handle pivots, means for synchronizing the position of said two cam members with respect to each other each rotatable about said jaw handle pivots and adapted for relative rolling motion, one on the other at their point of contact, the distance between said jaw handle pivot and the perimeter of each of said cams varying in accordance with a predetermined work force curve and means biasing the cam members into abutting contact with each other.

References Cited in the file of this patent UNITED STATES PATENTS 351,339 Pullman Oct. 19, 1886 444,635 Helwig Jan. 13, 1891 520,896 Porter June 5, 1894 884,680 Polakoskey Apr. 14, 1908 939,511 Jensen Nov. 9. 1909 

